Conventional file and/or stream formats for transmitting multiple data streams of varying media are limited in several respects. First, these formats are generally limited in the packet sizes that are available for encapsulating data. Such formats, if they specify packets, specify the packets as a given fixed size. Another limitation of such formats is that they do not facilitate the use of error correction codes. A further weakness of these conventional formats is that they do not provide flexibility in timing models for rendering the data encapsulated within the format. An additional limitation with such formats is that they are not well adapted for different transport mediums that have different levels of reliability and different transmission capabilities.